"It seems as it is specifying the interval in milleseconds totake the tokens and apply them to conform of the packet. Which means higher milleseconds cam mean higher processing time but lower drop rate."
It doesn't matter whether Bc is defined in bytes or milliseconds, basically they both cause the same effect.
"Higher" milliseconds I would expect to be more likely (but possibly not) to lead to lower processing time. As to effect on drop rate, that's an it depends answer.
Let's me explain another way of understanding how policing (and shaping) work.
Let's assume we have a 100 Mbps link but we want to transport data as if it were a 10 Mbps link. How do we do this?
For starters, always keep in mind the 100 Mbps link will always transmit at 100 Mbps (disregarding actual multi-speed interfaces).
We can make the 100 Mbps link behave (somewhat) like a 10 Mbps link if we somehow only allow it to transmit only 10% of the time.
Hmm, 10% of what time? A day, an hour, a minute, a second or some fraction of a second?
Starting with a second, as the time interval, a 100 Mbps link can transmit 100,000,000 bits in a second, while a 10 Mbps link can only transmit 10,000,000 bit a second. So, all we need to do, is count bits to be transmitted, each second, and drop (police) (or shape [queue]) any excess during each second.
Realize, during the second being measured, the 10,000,000 bits could all be transmitted during the first 100 milliseconds, the last 100 milliseconds, or scattered across the one second interval.
Every second, we start, again, checking bits to be transmitted again against our allocated amount of 10,000,000 bits for each second.
For what's I've just described, Tc would be 1 second and Bc would be 100 milliseconds or 1,250,000 bytes (NB: both 10% of the 100 Mbps link capacity for 1 second), i.e. Bc is the maximum amount of bits allowed to be transmitted during out Tc of 1 second, either as a total bit/byte count, or the (total) time to transmit that number of bits/bytes at physical link speed.
I'm not going to go into all the whys of selecting the Tc value (beyond noting a full second is probably very excessive), but suppose you wanted the Tc to be 10 milliseconds, while still emulating a 10 Mbps transmission rate. If so, as 10 millisecond is 1/100 of our prior Tc (of a second), Bc would also need to be 1/100, i.e. either 1 millisecond or 1,250 bytes.
If we want to emulate a 20 Mbps link (on the 100 Mbps link), while still keeping Tc at 100 milliseconds, Bc would be twice what is was, i.e. 2 milliseconds or 2,500 bytes.
